THE PRESENT INVENTION relates to a safety arrangement, and more particularly relates to a safety arrangement in a vehicle such as a motor car.
A substantial proportion of all fatal accidents involving motor vehicles are accidents in which the motor vehicle rotates through at least 90xc2x0 a around the longitudinal axis, the x axis of the vehicle. Such an accident is termed a roll-over accident.
The roll of the vehicle may be initiated by several different mechanisms. For example, the vehicle may slide into a curb or some other solid object, or may drive or slide into a ditch or down a slope. The vehicle may also slide across a surface which has a relatively high coefficient of friction, such as the surface of a road, or soil. For example, one or more wheels of the vehicle may slide into soil at the edge of the road. In the case of sliding into a solid obstacle or on to soil, the force that acts on the vehicle due to the contact of the wheels of the vehicle with the obstacle or the soil effectively xe2x80x9ctripsxe2x80x9d the vehicle into a roll-over.
In a typical roll-over accident there is a substantial risk that the driver or occupant of the vehicle will be ejected from the vehicle. Typical injuries that arise in such an accident are injuries to the head or face region, and in most cases these injuries are due to contact with the ground due to full or partial ejection from the vehicle.
It has been proposed to provide a safety arrangement in a motor vehicle in which an inflatable element is provided which, when inflated, forms a curtain that extends adjacent the driver or occupant of the vehicle, being located between the driver or occupant of the vehicle and the door or window opening at the side of the vehicle. An inflatable element of this type may be termed xe2x80x9can inflatable curtainxe2x80x9d. However, such an inflatable element must be inflated at an appropriate time to provide protection for the driver or occupant of the vehicle during a roll-over accident.
Whilst various sensors have been provided to initiate inflation of an inflatable element such as an inflatable curtain, it has been found that such sensors may not always provide an appropriate triggering signal for the deployment of the safety device, especially if the vehicle is involved in a soil tripped, or a curb tripped roll-over.
The present invention seeks to provide an improved safety arrangement.
According to this invention there is provided a safety arrangement in a vehicle, the safety arrangement comprising a safety device adapted to protect an occupant of the vehicle in the case of a roll-over accident, and a roll sensor arrangement adapted to provide a signal to trigger activation of said safely device, said signal being provided in case a roll or an anticipated roll of the vehicle is detected, the roll sensor arrangement being responsive to both
a) an angular parameter selected from the angular speed (xcfx89x) around the longitudinal axis of the vehicle, or the actual angle of roll (xcex1x) about the longitudinal axis of the vehicle, and
b) a velocity parameter relating to the vehicle speed selected from the total velocity of the vehicle, or the velocity of the vehicle in a predetermined direction. The total velocity of the vehicle may comprise the longitudinal velocity of the vehicle, and the velocity of the vehicle in a predetermined direction may comprise the lateral velocity of the vehicle.
Preferably said roll sensor arrangement is responsive to angular speed of the vehicle around the longitudinal axis of the vehicle, and is also responsive to the total velocity of the vehicle or a component of the velocity of the vehicle, such as the longitudinal velocity or the lateral velocity.
Conveniently the roll sensor arrangement comprises an angular speed sensor to measure said angular speed (xcfx89x) and a speedometer to measure the longitudinal velocity of the vehicle,
Advantageously the signal is generated only if the instantaneous angular speed of the vehicle reaches a predetermined threshold, the said threshold being a function of the velocity of the vehicle or the velocity of the vehicle in a predetermined direction.
In one embodiment the invention, the function of vehicle velocity is a function of the longitudinal velocity of the vehicle.
In an alternative embodiment the said function of vehicle velocity is a function of the lateral velocity of the vehicle.
Conveniently the angular speed of the vehicle is compared with a predetermined reference valve and, if the angular speed of the vehicle exceeds the reference speed, timing means are activated to measure a predetermined period of time, the timing means enabling the safety arrangement to permit triggering due to said velocity dependent threshold being reached only during the predetermined period of time.
Advantageously the signal is generated if the angular velocity (xcfx89x) exceeds a predetermined threshold which is a function of the total velocity of the vehicle, or a component of the velocity of the vehicle, or if the angular velocity exceeds a threshold which is a function of the existing roll angle of the vehicle.
Conveniently the sensor arrangement comprises means to determine the instantaneous lateral acceleration of the vehicle, and means to inhibit triggering unless the lateral acceleration of the vehicle exceeds a predetermined threshold.